ul {
	list-style-type: none;
	margin: 0px;
	padding: 0px;
	background-color: orange;
	width: 250px;
	text-align: center;
}

a:link,a:visited {
	text-decoration: none;
	background-color: orange;
	color: purple;
	width: 50px;
	text-align: center;
}

a:active,a:hover {
	background-color: green;
}

li {
	display: inline;/*一行展示*/
	padding: 3px;/*上下边距*/
	padding-left: 5px;
	padding-right: 5px;
	font-weight: bold;/*文字加粗*/
}